Optimal spilling for CISC machines with few registers

Andrew W. Appel, Lal George

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Many graph-coloring register-allocation algorithms don't work well for machines with few registers. Heuristics for live-range splitting are complex or suboptimal; heuristics for register assignment rarely factor the presence of fancy addressing modes; these problems are more severe the fewer registers there are to work with. We show how to optimally split live ranges and optimally use addressing modes, where the optimality condition measures dynamically weighted loads and stores but not register-register moves. Our algorithm uses integer linear programming but is much more efficient than previous ILP-based approaches to register allocation. We then show a variant of Park and Moon's optimistic coalescing algorithm that does a very good (though not provably optimal) job of removing the register-register moves. The result is Pentium code that is 9.5% faster than code generated by SSA-based splitting with iterated register coalescing.

Original languageEnglish (US)
Pages (from-to)243-253
Number of pages11
JournalSIGPLAN Notices (ACM Special Interest Group on Programming Languages)
Issue number5
StatePublished - May 2001

All Science Journal Classification (ASJC) codes

  • Software
  • Computer Graphics and Computer-Aided Design


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